TM6SF2 E167K

The Liver-Heart Trade-Off Gene

TM6SF2 (transmembrane 6 superfamily member 2) is a hepatic protein that facilitates
the loading of lipids onto very low-density lipoprotein (VLDL) particles |
VLDL particles transport triglycerides and cholesterol from the liver to the rest
of the body for export from the liver.
The E167K variant (a glutamate-to-lysine substitution at position 167) creates one
of the most interesting genetic trade-offs in human metabolism: it protects your
heart while putting your liver at risk.

The E167K mutation causes the TM6SF2 protein to misfold and degrade rapidly |
E167K reduces TM6SF2 protein levels by 46% in liver cells,
impairing the liver's ability to package and export fat. Triglycerides that should
leave the liver via VLDL particles instead accumulate inside liver cells, leading
to fatty liver disease. But here's the paradox: those same triglycerides that never
make it into your bloodstream mean lower circulating lipids and reduced cardiovascular
risk. You're trading liver health for heart health.

The Mechanism

TM6SF2 normally resides in the endoplasmic reticulum and ERGIC (ER-Golgi intermediate
compartment) | The ERGIC is where VLDL particles receive their lipid cargo before
secretion, where it helps load triglycerides
and cholesterol esters onto nascent VLDL particles. The E167K substitution disrupts
this process at a molecular level: the amino acid change from glutamate (negatively
charged) to lysine (positively charged) destabilizes the protein structure, leading
to accelerated degradation via the ubiquitin-proteasome pathway.

With reduced TM6SF2 protein, the liver specifically fails to assemble and secrete
large, triglyceride-rich VLDL1 particles | VLDL1-apoB100 production is markedly
reduced in E167K homozygotes, while smaller VLDL2 production remains normal.
VLDL1-triglyceride production drops by 35% in E167K carriers. The triglycerides
that can't be exported accumulate in hepatocytes as lipid droplets—the hallmark
of nonalcoholic fatty liver disease (NAFLD).

At the molecular level, E167K also impairs the liver's ability to synthesize
polyunsaturated phosphatidylcholines | E167K carriers have lower hepatic
polyunsaturated phosphatidylcholines despite higher total triglycerides,
particularly those containing omega-3 fatty acids. Recent research shows that
E167K increases the interaction between TM6SF2 and PNPLA3 | TM6SF2 E167K variant
decreases PNPLA3-mediated PUFA transfer to promote hepatic steatosis,
impairing PNPLA3's normal function of transferring polyunsaturated fatty acids
(PUFAs) from triglycerides to phosphatidylcholines. This disrupts membrane
lipid composition and exacerbates hepatic steatosis.

The Evidence

The E167K variant was discovered in 2014 through an exome-wide association study |
Kozlitina et al. Exome-wide association study identifies a TM6SF2 variant that
confers susceptibility to nonalcoholic fatty liver disease. Nature Genetics, 2014
of the Dallas Heart Study cohort. Carriers had significantly elevated liver fat
on MRI and higher ALT levels, but paradoxically lower plasma triglycerides and
LDL cholesterol.

A 2015 meta-analysis of 91,937 individuals | Pirola et al. The dual and opposite
role of the TM6SF2-rs58542926 variant. Hepatology, 2015
confirmed the paradoxical effects: T allele carriers had an odds ratio of 2.13
for NAFLD but showed protection against cardiovascular disease through reduced
circulating lipids. The effect size is substantial—among the strongest common
genetic risk factors for fatty liver disease.

Subsequent studies have shown that E167K is associated with the full spectrum
of NAFLD progression | TM6SF2 rs58542926 influences hepatic fibrosis progression.
Nature Communications, 2014: simple
steatosis, steatohepatitis (NASH), advanced fibrosis, and hepatocellular carcinoma.
A 2024 study found that E167K homozygotes have dramatically elevated risks |
OR 5.38 for steatotic liver disease, OR 5.76 for steatohepatitis, OR 11.22 for
hepatocellular carcinoma,
making this one of the highest-risk genotypes for liver disease.

A 2020 kinetic study using stable isotope tracers | Effects of TM6SF2 E167K on
hepatic lipid and very low-density lipoprotein metabolism. JCI Insight, 2020
in 10 E167K homozygotes revealed the precise mechanism: VLDL1-apoB100 production
was markedly reduced and VLDL1-triglyceride production was 35% lower compared to
controls. This impaired VLDL1 secretion explains both the hepatic fat accumulation
and the cardiovascular protection.

The cardiovascular protection is real: a 2024 community cohort study | TM6SF2-rs58542926
Genotype Has Opposing Effects on Incidence of Hepatic and Cardiac Events. Clinical
Gastroenterology and Hepatology, 2024
found that TT genotype carriers had a 3.16-fold increased risk of liver-related
events but a 0.76-fold reduced risk of major adverse cardiovascular events. In
most risk groups, the absolute decrease in cardiovascular events exceeded the
absolute increase in liver-related events.

Practical Implications

If you carry the T allele, your liver is vulnerable but your heart has a genetic
advantage. The key is to support your liver proactively while recognizing that
you don't face the same cardiovascular lipid burden as non-carriers.

Diet matters more for you than for most people. Animal studies show that
dietary phosphatidylcholine containing C18:3 fatty acids | Dietary PC containing
C18:3 completely abolished liver damage from E167K in high-fat diet-fed mice
can completely prevent E167K-induced hepatic steatosis and injury. Choline
(found in eggs, liver, and soybeans) is a precursor to phosphatidylcholine, and
dietary choline restriction increases liver fat in humans | Circulating
triacylglycerol signatures and insulin sensitivity in NAFLD. Journal of Hepatology,
2015.

Your genotype makes you particularly sensitive to high-fat diets. Studies show
that caloric restriction can override the prosteatotic effects | Reduction of
caloric intake might override the prosteatotic effects of PNPLA3 and TM6SF2
variants. PLoS ONE, 2016 of E167K.
Weight management is not optional—it's essential liver protection for T allele
carriers.

Monitoring is critical. E167K carriers show significantly elevated ALT and AST
levels | Meta-analysis of the influence of TM6SF2 E167K variant on plasma concentration
of aminotransferases. Scientific Reports, 2016
even before NAFLD is diagnosed. Regular liver enzyme testing can catch early
damage. Liver imaging (ultrasound or MRI) every 2-3 years helps assess steatosis
progression before it advances to fibrosis.

The lipid paradox has clinical implications. Your naturally lower LDL and
triglycerides mean you may not need aggressive lipid-lowering medications that
others require. Discuss your genotype with your physician when considering statin
therapy—the risk-benefit calculation is different for E167K carriers. However,
don't assume your favorable lipid profile means you're metabolically healthy; your
liver may be accumulating fat that never shows up in standard lipid panels.

Interactions

The TM6SF2 E167K variant shows strong additive effects with PNPLA3 I148M | The
additive effects of the TM6SF2 E167K and PNPLA3 I148M polymorphisms. Oncotarget,
2017. When both variants are present,
liver fat accumulation and fibrosis risk increase substantially beyond either
variant alone. The 2024 mechanistic study | TM6SF2 E167K variant decreases
PNPLA3-mediated PUFA transfer. Clinical and Molecular Hepatology, 2024
showed that E167K increases the interaction between TM6SF2 and PNPLA3 proteins,
impairing PNPLA3's ability to transfer polyunsaturated fatty acids from triglycerides
to phosphatidylcholines. This protein-level interaction explains why the two
variants compound each other's effects on hepatic steatosis.

Other NAFLD-risk variants also interact with TM6SF2: MBOAT7 rs641738, GCKR
rs1260326, and HSD17B13 rs72613567 | Combined effects of PNPLA3, TM6SF2 and
HSD17B13 variants on severity of biopsy-proven NAFLD. Hepatology International,
2021 have been
studied in multi-variant genetic risk scores. MBOAT7 primarily affects fibrosis
progression, while HSD17B13 appears protective against inflammation. These genes
are linked through protein-protein interaction networks | TM6SF2 co-expressed
with GCKR and HSD17B13, PNPLA3 co-expressed with GCKR,
suggesting shared lipid metabolism pathways.

An interesting gene-diet interaction has been documented: the protective effect
of a "Prudent" dietary pattern | TM6SF2-rs58542926 modifies the protective effect
of a prudent dietary pattern. Nutrients, 2023
rich in unsaturated fatty acids on serum triglycerides is significantly modified
by E167K—T allele carriers may not benefit from this dietary pattern the way
CC carriers do.